I couldn't get Ittis to work for Iris; their absorbency isn't up to much for a heavy wetter. And if I tried to boost it, it meant a dreadful fit.
DD is a heavy wetter. We used fitteds and wool 95% of the time; I've changed our stash and now only have 6 pockets (for DH to use). Those I stuff with a hemp Wonderfulls, Easy Peasy hemp booster and Babeco bamboo booster. And that combo just about lasts 3 hours. For heavy wetters, lots of people find bamboo fitteds and wool the best option.